This bug was originally marked as duplicate of bug 185346, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.
Build: NetBeans IDE 7.3 Beta 2 (Build 201211062253)
VM: Java HotSpot(TM) 64-Bit Server VM, 23.6-b04, Java(TM) SE Runtime Environment, 1.7.0_10-b18
OS: Windows 7
GUEST: I try to rename folder from "Send" to "send" with no result. Then I try to rename to some other name -- folder was renamed. But I can't rename this folder again to "send" -- this error occures.
java.lang.AssertionError: childName: C:\Www\Crm\nbproject folderName: C:\Www\crm
Created attachment 129748 [details]
I'm sorry, I cannot reproduce the bug.
Please, can you try to reproduce it in the latest development build
and reopen the issue if the bug is still valid?